Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/1/2004
Publication Date: 7/1/2004
Citation: Snodgrass, G.L., Abel, C.A. 2004. Effect of host plants species on diapause in tarnished plant bug. National Cotton Council Beltwide Cotton Conference. Interpretive Summary: In the mid-South the tarnished plant bug is a key pest of cotton in which it is controlled exclusively with insecticides. Because of increasing amounts of resistance to insecticides, alternative non-insecticidal control methods are needed for plant bugs. The development of these alternative control measures require a thorough knowledge of the basic biology of plant bugs in the mid-South. Tarnished plant bugs overwinter as adults in diapause which is a non-reproductive state in which large amounts of fat are accumulated to allow them to survive the winter until food becomes available. Diapausing adults are produced on wild host plants in the late summer and fall. A reduction in the numbers of these overwintering adults could be a goal of alternative control measures. These control methods could include cultural control of wild hosts, treatment of plant bugs on wild hosts with entomopathogens, or release of plant bug parasites and/or predators on the host plants. Knowledge of which host plant on which to target developing plant bug populations is essential for development of alternative control measures which reduce numbers of overwintering adults. In the current study, the percentages of plant bugs that developed into diapausing adults each week on six abundant late summer and fall host plant species were determined in 2002 and 2003. These data will be very useful in determining when to begin using an alternative control method and which host plant species to target. Percentages in diapause were affected by host plant species, and consistently higher numbers of diapausing adults were produced on pinkweed as compared to pigweed, horseweed, giant ragweed, goldenrod, and white heath aster. Host plant quality was also thought to influence numbers of diapausing adults produced, and host quality was thought to be affected by temperature and rainfall.
Technical Abstract: Fourth and fifth instars of the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), were collected from wild hosts in the fall and reared in the laboratory to adults using their collection host as food. Adults were dissected when 7 d of age or older to determine whether they were reproductive or in diapause. Nymphs reared on pigweed, Amaranthus spp., goldenrod, Solidago altissima L, and white heath aster, Aster pilosus Willdenow, in October and early November 2002 produced adults which ranged from 48 to 80% in diapause. Adults from rearing nymphs on these same host species in October 2003 were mostly (>95%) in diapause. The lower percentages of adults in diapause found in 2002 were thought to be the result of higher quality of the host plants caused by excellent growing conditions (above average temperatures and rainfall). The percentage of adults in diapause produced on pinkweed, Polygonum pensylvanicum L., was consistently higher in both years compared to the percentages of adults in diapause found on the other hosts. Pinkweed grows primarily in wet areas in or near ditches and the quality of this host was probably less affected by temperature and rainfall than the other hosts. Reproductive females reared from all hosts in September had lower amounts of fat than reproductive females reared from these hosts in October and November. The fat content of the reproductive females reared in October and November was characteristic of adults in diapause, although their ovaries were expanded with mature or developing eggs and/or they were recently mated. The role that the reproductive females produced in October and November play in the adaptation of plant bugs to their winter habitat is unknown. Host plant species was found to influence the percentage of adult plant bugs which entered diapause in September through November in the mid-South, and host plant quality was probably another determining factor.